A vote recount Thursday in Mexico confirmed a wide margin of victory for Enrique Pena Nieto, but tensions simmered over allegations of vote buying in last weekend’s presidential election.

Police amassed outside the compound of the Federal Election Institute as authorities nearly finished a recount of more than half of the 49 million votes cast on Sunday.

Supporters of the second-place finisher, leftist Andres Manuel Lopez Obrador, allege that activists with Pena Nieto’s Institutional Revolutionary Party bought votes with gift cards from a grocery chain in the capital, part of the surrounding state of Mexico and in the state of San Luis Potosi.

Pena Nieto, in an interview with the BBC’s Spanish-language service, denied that his party had bought votes and suggested that Lopez Obrador was a poor loser.

By early afternoon, electoral authorities said they had concluded 96 percent of the recount, and results did not vary significantly from those that led Pena Nieto to declare victory Sunday night.

Pena Nieto won 38.3 percent of the vote and Lopez Obrador 31.4 percent. A third candidate, Josefina Vazquez Mota of the ruling National Action Party, tallied 25.4 percent, and a fourth candidate, Gabriel Quadri de la Torre of the National Alliance, pulled in 2.3 percent.

The margin of nearly 7 percentage points that Pena Nieto held over Lopez Obrador – who lost the 2006 presidential race by a margin of less than 1 percent and led a six-week blockade of the capital’s main boulevard for what he claimed was fraud – appeared to be convincing despite the allegations of vote buying.

The Federal Electoral Institute is expected to make a formal announcement this coming weekend of the official winner.

Lopez Obrador’s supporters posted videos to YouTube of angry shoppers flocking to stores of the Soriana grocery chain in fear that gift cards they said they’d been given by PRI officials contained less value that they’d been promised.

Frantic shoppers emptied shelves in Soriana branches in Ecatepec and Iztapalapa using the gift cards. La Jornada, a leftist newspaper, said people who’d received gift cards in San Luis Potosi complained that the cards held only 100 pesos in value (about $7.50) instead of the 1,000 pesos they’d been promised.

Pena Nieto, in a series of interviews, said the videos were likely doctored and that the allegations came from opponents of the PRI, which ruled Mexico for 71 consecutive years until 2000, when it lost power and went into a hibernation of sorts until Sunday’s vote.

In the interview with BBC Mundo, Pena Nieto said Lopez Obrador has contested both of his losing presidential elections. “I really lament that the leftist candidate doesn’t recognize the results,” he said.